In Texas, it is legal for someone under 21 to drink alcohol under their parents supervision whether it be in private at their dinner table or at an establishment that serves alcohol. (Restaurant, Nite Club/Bar that allows under 21 in, a sporting event, etc)
Sec.106.04. CONSUMPTION OF ALCOHOL BY A MINOR
(a) A minor commits an offense if he consumes an alcoholic beverage.
(b) It is an affirmative defense to prosecution under this section that the alcoholic beverage was consumed in the visible presence of the minor's adult parent, guardian, or spouse.
TABC Alcoholic Beverage Code Referencing Minors
Parents get into trouble with the law when they serve alcohol to their childs "Friends". That's what comes into play when you hear the stories on the news about parents serving alcohol to minors. It's usually serving children other than their own that they're getting into trouble for.
My opinion, I'd like to see the drinking age raised to 25 all over the country. Also, I'd like the voting age raised to 21.
My exception is just like most here. If a guy/gal voluntarily joins the Military at age 18-25, then they should also have the right to consume alcohol. BUT, on base only, like at the NCO Club.
Big difference between "civilian" and "military" 18-25 year olds is that there's a lot more supervision when one is in the Military. Most "Privates" (E1's) through "Specialists" (E4"s) are supervised 24/7 in the Military, while the civilian 18-25 year olds run willy nilly at all times. If you compare the maturity level of a 20 year old that has 2 years Military service with the maturity level of a 25 year old who's run willy nilly since high school/college, you will find that probably the 20 year is much more mature when it comes to everyday "Life" decisions.